cifs: Fix memory leak when using fscache

[ Upstream commit c6f62f81b488d00afaa86bae26c6ce9ab12c709e ]

If we hit the 'index == next_cached' case, we leak a refcount on the
struct page.  Fix this by using readahead_folio() which takes care of
the refcount for you.

Fixes: 0174ee9947bd ("cifs: Implement cache I/O by accessing the cache directly")
Cc: David Howells <dhowells@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 58dce567ceaf1c3768f556dcf5206a095317ff27..3d475f1847a4f859333d2e9f54b82d401ba7071c 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4456,10 +4456,10 @@ static void cifs_readahead(struct readahead_control *ractl)
                                 * TODO: Send a whole batch of pages to be read
                                 * by the cache.
                                 */
-                               page = readahead_page(ractl);
-                               last_batch_size = 1 << thp_order(page);
+                               struct folio *folio = readahead_folio(ractl);
+                               last_batch_size = folio_nr_pages(folio);
                                if (cifs_readpage_from_fscache(ractl->mapping->host,
-                                                              page) < 0) {
+                                                              &folio->page) < 0) {
                                        /*
                                         * TODO: Deal with cache read failure
                                         * here, but for the moment, delegate
@@ -4467,7 +4467,7 @@ static void cifs_readahead(struct readahead_control *ractl)
                                         */
                                        caching = false;
                                }
-                               unlock_page(page);
+                               folio_unlock(folio);
                                next_cached++;
                                cache_nr_pages--;
                                if (cache_nr_pages == 0)